The general objective of the proposed research is to pursue secretory physiology by studying various aspects of those factors determining the composition of cochlear fluids. Specifically, it is planned to study the relationship between the effect of diuretic agents on the composition of endolymph and catecholamines and their blocking agents. In addition, it is planned to measure the pH of endolymph using ultra-micro glass electrodes as the first step in studying the penetration of weak organic acids and bases into the scala media. It is also hoped that a study can be made of the relationships between alterations of the composition of endolymph and the endolymphatic potential and the hydrostatic pressure within the scala media.